Project 2 Will use RIP 1-Tag2 transgenic mice as a prototypical mouse model of multistage carcinogenesis, wherein targeted expression of dominant oncogenes (encoded by the SV40 early region) to endocrine pancreas elicits a pathway to invasive carcinoma. The focal distribution of the target tissue into approximately 400 nodules has allowed the pathway to be described with unprecedented clarity: normal oncogene-expressing islets progress to hyper-proliferative islets, of which a subset switch on angiogenesis, and again a subset progress to encapsulated tumors and invasive carcinomas. The synchronicity of stepwise progression, the complete penetrance of cancer by 12 weeks of age, and the statistical opportunities afforded by the 400 islets at risk, have collectively allowed design of distinctive preclinical trials targeted to different stages of disease progression. Remarkably, several first-generation metalloproteinase inhibitors showed stage specific efficacy, being effective at early but not late stage disease targets. The data suggest that protease inhibitors can be used to probe the functional importance of proteases in different stages of carcinogenesis, instructing about mechanisms and perhaps influencing future consideration and design of clinical trials involving protease inhibitors. Recently, preliminary studies with the Biochemistry Core have demonstrated that a heretofore under-appreciated class of protease, the Clan CA cysteine proteases (i.e. cathepsins), are upregulated in activity and functionally contributing to islet carcinogenesis. This project will focus on that exciting observation, investigating the involvement of cathepsins in the islet carcinoma model as well as a model of prostate cancer. The goals are: Aim 1. Address the hypothesis that cathepsins (Clan CA cysteine proteases) are making specific functional contributions to the distinctive stages of islet carcinogenesis. Aim 2. Assess the possible involvement and functional contributions of cysteine proteases in a model of prostate carcinogenesis. Aim 3. Audit gene expression and activity profiles of metallo-, serine, and aspartyl cathepsin proteases in the RIP-Tag model, with the goal of identifying additional candidate proteases involved in this prototypical carcinogenesis pathway.